Magnetic drawing boards have been introduced to markets for many years. They are a popular form of erasable drawing board which in many times serve as a replacement for conventional drawing utensils such as ink and crayons. Parents consider that magnetic drawing boards provide a cleaner and safer alternative for their children to draw. Magnetic drawing boards are now common toys for children and very often they serve educational purposes.
A typical magnetic drawing board found in the market is the one which comprises mainly an upper substrate forming a magnetic display panel, a lower substrate, and a honeycomb structure sealedly arranged therebetween with each cell of the honeycomb structure encapsulated with a dispersion medium and magnetic particles. When a user draws a line on the upper substrate with a magnetic pen, the magnetic particles in the cell underneath the point of contact between the tip of the magnetic pen and the upper substrate will be drawn upwards towards the upper substrate, thereby forming a line on the upper substrate. When a user uses the magnetic eraser (usually in form of a magnetic strip slidably attached to the lower substrate) to remove the line, the magnetic particles in the cell on top of the point of contact between the magnetic eraser and the lower substrate will be drawn downwards towards the lower substrate, thereby rendering the line on the upper substrate to disappear.
In some magnetic drawing boards, it is possible to attain multi-color display. In such case, the drawing board is divided into a number of areas, and the cells in each area are encapsulated with magnetic particles of a color specific for that area. Therefore, when the user draws a line on the upper substrate with a magnetic pen in one area in which the cells are encapsulated with magnetic particles of a specific color, the line appeared on the upper substrate will be in that specific color in that area.
The existing method to manufacture the aforementioned magnetic drawing board with multi-color display is as follows: (1) the honeycomb structure is attached to the lower substrate; (2) a mesh which is partitioned into a plurality of areas is placed on top of the honeycomb structure, and each of the areas is designated with a specific color; (3) magnetic particles of the specific colors are placed onto the corresponding areas of the mesh designated with corresponding specific colors, so that all areas of the mesh are filled with magnetic particles of corresponding specific colors; (4) the magnetic particles are brushed to pass through the mesh and fall into the honeycomb structure, so that all cells in the honeycomb structure are correspondingly filled with magnetic particles of specific colors; (5) the cells are then filled with dispersion medium; (6) finally the upper substrate is sealingly attached onto the honeycomb structure. The existing method is disadvantageous in that it is impossible to achieve fine division of areas of different colors. This is because when the magnetic particles of a specific color pass through the mesh and fall into the cells of the honeycomb structure designated for that specific color, some of the magnetic particles may escape to adjacent cells designated for a different color through gaps between the mesh and the honeycomb structure. As a result, the border of the areas of different colors is always unclear as the cells contain magnetic particles of different colors. As a result, there is a limit on the size and shape of the areas of different color.